1. Field of the Invention
The present invention relates to a method of resin molding and a resin molding machine. More precisely, the present invention relates to a method of resin molding comprising the steps of: providing release film, which is capable of easily peeling off from molding dies and resin, on a parting faces of the molding dies; and clamping a member to be molded by the molding dies together with the release film, and a resin molding machine for executing said method.
2. Description of Background Art
A conventional resin molding machine is shown in FIG. 16. In the conventional machine, a member to be molded is clamped between an upper die 10a and a lower die 10b. Resin heated and melted in a pot 12 is pressurized and sent to a cavity 14 by a plunger 13. Resin tablets, which are formed by: kneading resin materials; forming the resin kneaded into granules and compressing the granular resin to form into the tablet shapes, are used as resin for molding.
The resin sent from the pot 12 directly contacts molding faces of the molding dies, so the molding dies are made of abrasion-proof metal with enough durability. The conventional molding dies have ejector pins 16, which eject a molded product from the molding dies.
Thermosetting resin, e.g., epoxy resin, phenolic resin, are usually used for the resin molding. Generally, the resin is required to be easily peeled off from the molding dies and to tightly adhere to the member to be molded, e.g., a lead frame. However, said required conditions of the resin are mutually contradictory, so that the resin which properly satisfies required conditions is selected. Actually, characteristics of the resin must be one-sided. For example, when one resin, which is capable of very easily peeling off from the molding dies, is used for the molding, the solidified resin is apt to peel off from the member to be molded.
On the other hand, when another resin, which has greater adhering force, is used, the solidified resin is not capable of easily peeling off from the molding dies. And some ejector pins cannot be moved, so that the molded product cannot be ejected from the molding dies. Further, when gates are broken after molding, solidified resin, which is solidified in the gates or runners, is left on a surface of the molded product, e.g., a lead frame.
An object of the present invention is to provide a method of resin molding for molding said regular products and a resin molding machine for the same. Compared with the conventional molding method and the molding machine, the present invention is capable of making molding quality higher and decreasing manufacturing cost of the products.
To achieve the object, the method of the present invention comprising the steps of:
covering at least an inner face of a pot of molding dies with release film, which is capable of easily peeling off from the molding die and resin;
supplying a resin tablet into the pot; and
clamping a member to be molded between the molding dies to mold.
In this method, the molding can be executed without using the wrapped resin.
In the method, the covering step may comprise the steps of:
covering over the face including a cavity, a cull and a pot with a sheet of the release film; and
sucking the release film to fix onto a part of the face for clamping the member to be molded, an inner face of the cavity, an inner face of the cull and the inner face of the pot.
And in the method, the covering step may comprise the steps of:
covering over the face including a cavity, a cull and a pot with a sheet of the release film; and
sucking the release film to fix onto the face for clamping the member to be molded, an inner face of the cavity and an inner face of the cull;
providing the resin tablet onto the release film at a position corresponding to the pot; and
setting the resin tablet in the pot by closing the molding dies.
In the method, the release film may have an accommodating section into which the resin tablet is supplied, and the accommodating section may be formed to correspond to an inner shape of the pot. In this case, unwillful shift of the release film on the molding dies can be prevented.
In the method, the accommodating section may be formed in the release film before providing the release film on the face of the molding die.
If the resin tablet is preheated in the accommodating section, and the resin tablet is supplied together With the release film, the molding quality can be improved.
Further, in the method, a resin path, which passes over an opening section of the pot and the member to be molded, may be covered with additional release film. In this case, the molding can be executed without adhering surplus resin to the product.
On the other hand, the molding machine of the present invention comprises:
molding dies capable of clamping a member to be molded;
a pot for sending resin melt to cavities of the molding dies with pressure; and
a fixing mechanism for fixing a sheet of the release film on the face including a cavity, a cull and the pot,
wherein release film, which is capable of easily peeling off from molding dies and resin, is provided on faces, which include the cavities, of the molding dies.
In the machine, the pot may be capable of accommodating the stick-type resin tablet. And the molding die may have a plurality of pots, which are capable of accommodating the columnar resin tablets.
Furthermore, the machine of the present invention comprises:
molding dies;
a pot being formed in the molding die; and
a film forming mechanism being provided on the film-supplying side of the molding dies, the film forming mechanism being capable of forming an accommodating section, into which the resin tablet is supplied, in the release film,
wherein an inner face of the pot is covered with release film when molding is executed. With this machine, the release film having the accommodating sections can be supplied to the molding dies, so that continuous molding can be executed.
The machine may further comprise a preheating mechanism for preheating the resin tablet which is accommodated in the accommodating section.
Further, the machine may further comprise an additional film forming mechanism for forming an additional release film, which is capable of covering over a resin path, which passes over an opening section of the pot and a member to be molded.